1. He writes his dialogues like he's writing script for novel/series/movie
2. Mixing drama with comedy, if you know how to do it, is ultimate recipe for engaging story
3. He took his time to build characters with their own unique trait & personality
4. He paid attention to little details
5. His models aren't exactly S tier (like Oceanlab, etc.) but he sure knows how to render animation
Many tries to copy DPC, whether its about doing Episodic update, campus/frat-house themed, etc. But they don't really seem bother to copy all 5 points above, especially in the writing part.